I played through one of these at the weekend and was very impressed with the sound and volume it put out. The band was playing rock, and consisted of a keyboard player, a guitarist going through a 50 watt, Marshall valve combo and a loudish drummer.
I got up and played a few songs during the break, with my country band and the amp sounded nice close up and really full and deep out front (with the master only half way up) I even got a compliment from another musician, in the audience, on the sound of the bass.
The amp wasn't on the floor, it was sitting on a wide, window ledge at about hip height. So there wasn't any coupling effect with the floor to enhance the bass frequencies but I could feel the bass through the soles of my shoes.
I've also played through the original Promethean P5110 and I actually preferred the sound of the P3110.
Looking at some of the comments previously, there doesn't seem to be a lot of love for this combo. But now, after hearing it in action, I'm seriously thinking about buying one.
Oh and by the way, the owner traveled to his gig by bus. That's how portable it is.